Image sensors have become ubiquitous. They are widely used in digital still cameras, cellular phones, security cameras, as well as, medical, automobile, and other applications. The technology used to manufacture image sensors, has continued to advance at a great pace. For example, the demands of higher resolution and lower power consumption have encouraged the further miniaturization and integration of these image sensors.
Pixel crosstalk is a limiting factor in the performance of semiconductor based devices. Ideally each pixel in an image sensor operates as an independent photon detector. In other words, electron/hole content in one pixel does not affect neighboring pixels (or any other pixels in the device). In real image sensors, this is not the case. Electrical signals couple to each other, and charge may spill from one pixel to another. This crosstalk may degrade image resolution, reduce image sensor sensitivity, and cause color-signal mixing. Additionally, defects at semiconductor interface(s) may result in dark current. Unfortunately, many solutions to crosstalk often exaggerate the effects of dark current or contribute to it. Ultimately this combination of dark current and crosstalk may lead to appreciable image degradation.
Accordingly, to mitigate the effects of crosstalk/dark current and enhance image sensor performance, many techniques have been employed. Some of these include using heavily doped regions to isolate individual pixels and employing post-acquisition algorithms to reduce image noise. However, both of these methods still cannot entirely eliminate the effects of pixel crosstalk and dark current.